 So thank you very much. It's a real pleasure to be here at the at this ancestral health symposium. I really First of all, it's wonderful to see such a healthy group of people Normally, I don't lecture to such an outrageously good-looking audience But the other the other thing is it's nice to have this here on the East Coast I wasn't able to go last year and in my backyard and as I was working on this This this lecture In the last few days I was in the field with a graduate student and he looked over at my title slide because I Kind of obsessed about title slides and I was trying to figure the right image in the right photo And he said you can't use that title. You're ending a sentence on a preposition and it reminded me One of those stupid Harvard jokes and there are a lot of bad Harvard jokes about how snobbish a place we are So there's the story about you can pick your stereotype. Let's just pick for the sake of a Stereotypes Texan so a Texan comes to visit Harvard. I'm sorry. I'm not trying to insult Texans here by the way This is actually an anti-Harvard joke not an anti-Texan joke So this Texan comes to Harvard and says where is the statue of John Harvard at and the snobby Harvard student says Here at Harvard. We don't end sentences on prepositions. So the guy scratches his chin says alright Where is the statue of John Harvard at asshole? So I hope Anyway, I've committed that sin, so here we are anyway It's real pleasure to be here and I study human evolutionary biology I'm the chair of the department here actually and and my interest really is in how and why the human body is the way it is But also why that matters for human health today So this really fits very nicely with some of the questions I'm interested in and when you think of the term ancestral health because I spend a lot of time worrying about ancestors, right? The question arises really how can we use information about human evolution but also principles of evolutionary medicine to improve human health And well-being I mean a lot of times we spend a you know a lot of effort in my field trying to figure out who begat whom But really who cares who begat whom really what matters is how we use our bodies how we live our lives And that's what really is most important So really that brings up the question. What are we adapted for? What's what's the nature of adaptation and as an evolutionary biologist? I can tell you it's much easier to answer what we're not adapted for we all have our favorite favorite things You know whether or not we should be eating you know giving our children big gulps or whether or not You know high-heeled shoes or or segues etc when how many heart attacks is this guy had I can't remember But anyway the point is it's easy to answer that question It's much smarter much harder is to answer the question what we're adapted for and and that's led of course to the prevalent Hypothesis out there, which is that many of the illnesses that we confront today in our society Perhaps 70% of the US healthcare budget goes towards what we call mismatch conditions Those are problems cause it caused by using the body in ways for which it was not adapted But what exactly do we mean by the term adaptation? It turns out that in evolutionary biology if you want to get five evolutionary biologists Mad or a room of evolutionary biologists mad you just use the word adaptation. It's a loaded word It's like putting a red flag in front of a bowl. It's actually worse because the bull probably can't see the red But anyway It leads to a series of major debates as to for example What isn't an adaptation in the first place how do we recognize adaptations and finally how do we reconcile the? conflicting trade-offs between different kinds of adaptations adaptation is not a simple concept So what I thought it would be a kind of fun to do would be to start off this symposium by thinking about this fundamental evolutionary question What's an adaptation? Talk about how I think it's relevant to the to the problems of evolutionary medicine and then give a kind of a case study that Obsesses me which is which is physical activity or for really now inactivity as a complex human adaptation So let's begin with the problem of adaptation so of course we everything and in evolution really goes back to Darwin and So remember let's I'm sure this is old hat for almost everybody in this room Just remember the basic theory of natural selection, which is three and it's three basic observations that Darwin made The first is that within any population just like this population here There's a lot of phenotypic variation. You all look different from each other Obviously and that many of those variations are heritable, right? They're passed from from ancestor to descendant So they have a genetic basis not a complete genetic basis a complex genetic basis based on on gene environment interactions And then finally there there's competition between organisms for limited resources now these none of these are comp are really Contentious issues even creationists probably believe in all three of these these conditions But what Darwin noted was that if you accept one two and three then the emergent outcome of all three of those the Combination all those three things is differential non random success That is within populations Individuals with more favorable phenotypic variations or actually often it's less Unfavorable phenotypic variations are gonna be more successful in surviving and reproducing and then they are naturally selected That's the basic theory of natural selection Now that theory leads to some important key concepts now One of the key concepts is fitness, which is obviously not just how many sit-ups you can do But actually is the relative stress on the word relative ability of an organism to survive and transmit its genes of the next generation so here's Mitt Romney and his family and I Don't know if Mitt Romney believes in evolution this week Versus next week, but even he would probably admit that he has a pretty high relative fitness right compared to say me I've only got one daughter and so he's got me beat in both the fitness category as well as the financial success category I'm sure there's some other categories. I win, but anyway But then the other issue the related issue is adaptation right now The common definition of adaptation out there is a useful feature that promotes survival and reproduction But remember we're taking an evolutionary perspective and that definition actually doesn't bring in Evolution and natural selection and so a better definition is a useful feature that has been shaped by natural selection That promotes survival reproduction. I'll explain in a while why that that is is is important So this leads to some important implications Now one of them of course is that adaptations are context specific, right? It depends on the environment the habitat the competitors all kinds of factors as to what's an adaptation A very classic example are the studies of Darwin's finches in the Galapagos That you might say well having a big beak is an adaptation But actually a big beak is an adaptation when the conditions are dry when conditions are wet Actually having a smaller beak is an adaptation. So there's a constant Shift between this being more adaptive and that being more adaptive and if any of you know the work of the grants They've shown that there's shifting selection Sometimes selection for thicker beaks and sometimes selections for less thick beaks And we actually know all the molecular mechanisms of the genetic Heritabilis et cetera that that give that give rise to these shifts in phenotype in this population A second important point is that all adaptations all of them involve trade-offs, right? There are costs and benefits that vary for every single aspect of your body There are many examples and one example that I'm for example very interesting is is stature, right? They're short people and tall people in the world and there's advantages and disadvantages of being short and being tall For example, that affects heat retention and the cost of of walking and running etc And you trade them off and so in different environments You're trading off some costs and benefits versus other costs and benefits for their net effect on your relative fitness In addition adaptations are imperfect We often have a kind of a glorified view of a natural selection being this incredible engineer And yes natural selection is a better engineer than any engineer that I know of but still it doesn't create perfection It simply drives animals towards better solutions in a particular context So natural selection drives structures towards optima very rarely achieves optimality Um, there are a few interesting cases where it does and we can talk about that over the bar That drinks in the bar And in addition, it's important to know that there's and this is also a source of vigorous debate that not all variations are adaptations Now I do a lot of work on the head and the skull and I can tell you that the head is loaded with features that are Are problematic as adaptations for example in well more than a hundred years of research Nobody's ever come up with a convincing adaptive explanation for why humans are unique in having a chin Um Broward is we're long thought to be adaptive for all kinds of reasons structurally etc But it turns out that brow rigid are simply the bright product of sticking a face out in front of the brain case It's just a byproduct of the relative position of the face relative to the brain case Um, we also have inherited relics that we no longer use There are probably a lot of you in this room who don't have your third molars And it probably has no effect whatsoever on your fitness right lots of people even have third molar a genesis So there are lots of variations in the body that are that are not adaptations And we have to be careful not to assume in fact Generally, we set the by heart in evolution high in evolutionary biology Which is that unless you can prove otherwise something is not an adaptation Not everybody subscribes to that view, but it's a useful Stance to take when you're trying to analyze the body So as an example for example, I'm very interested in the fact that humans have very short oral cavities And there's a wide Range of conflicting ideas about why we have short oral cavities One might be because it's a result of changes in the head that result from changes in brain shape It could be an adaptation for speech. It could be an adaptation for thermoregulation It could be an adaptation for sexual selection because nobody likes a long muzzle and a mate. Who knows? There's lots of ideas and if any of you really want to learn all the nitty-gritty of this This is a fantastic book that you can buy in the coop just in harvard square for $39.99 Which I will tell you all those just so stories of which you should be aware So why should this symposium and the society care about all those Negative things I've just said about adaptation and that really brings up Why is the theory of adaptation relevant to evolutionary medicine? Which is really what I think this symposium is all about so As a way of trying to describe this I'm going to try to Percent five principles which I hopefully will be useful For as a framework for much of the discussions that will fall in next few days And I will try to apply them to the the question of physical inactivity So the first principle as I think one that's very obvious to everybody in this room I don't think I need to um I don't think I need to convince anybody here Which is that a lot of modern illnesses are mismatch conditions That is problems caused by using the body in ways for which it is not adapted and we all have our favorites, right? Many of you may know that I'm obsessed with shoes or lack thereof And um, um just came back from collecting data on the effects of shoes on foot health Overuse of antibiotics too much sugar soft mattresses There's a long list of of ills and problems that are caused in today's world By using our bodies for ways in which we're not adapted That's the easy part There it gets more complicated though because it's important to remember that adaptations evolve not necessarily to promote fitness And remember i'm talking about fitness and the mit romney sense and relative reproductive success Not health, right? We didn't evolve to be healthy. We evolved to have more kids relative to somebody else That's what natural selection is all about So an obvious example that is human fatness, right? Humans are a very strangely strange mammal a very strange primate because we're really kind of fat Your typical primate primate is about five to maybe seven percent body fat, but human females We hunter-gatherers for example have about 15 to 20 percent body fat. We have very fat babies And it's a very interesting story. It's another lecture really about why humans are so fat But it has a lot to do with Trying to pay for really big brains and also trying to pay for a really unusual reproductive schedule In which we basically pump out babies twice as fast as chimpanzees and that requires Storing a lot of energy in order to pay for those expensively brained babies, etc Another story but in order to be fat, of course that leads to of course cravings for sugar and other calories Which then can lead to all kinds of health consequences that are very negative not only now but perhaps also in the past Now as an example, there's a very famous experiment in the gambia where it was an experiment It was a health study done in the gambia where back in the I think it was the 60s or the 70s It was the 70s the British government started providing nutritional supplements to undernourished malnourished mothers in the gambia In order to improve The health of their babies are a lot of low birth weight babies The result of the nutritional supplements was not to improve the health of the babies or the mothers But rather to increase the rate at which they reproduced that's the that's the prediction of natural selection That these adaptations evolved not to make us healthy, but to make us reproduce better Another important principle is that there was no single environment of evolutionary adaptiveness I know everybody in this room knows that But it's worth reminding ourselves that the body is a jumble of adaptations from the heads to our toes From the from the outside to the inside you have lots and lots of adaptations But they're not all in sync and they accrued in a complex way and a nice analogy that I like to use At the body is like a palimpsest. So a palimpsest is a is an ancient manuscript There are these old vellum manuscripts and the and the leather was so Valuable that they used to just scrape off the writing and write all over it again And then sometimes the writing would sort of fade and you'd get text in which there's multiple Multiple texts that are kind of all combined on the same page I think it's a useful analogy for the body because our body is like that and I'll give an example So for example, think about diet. What are we adapted to eat? I'm sure there'll be lots of discussions and future lectures about that today But we're actually adapted to eat a wide variety of foods that result from a long evolutionary history So we evolved from Animals that were primarily frugivores. So we evolved like chimpanzees to eat a lot of ripe fruit We still do and that's still healthy for us But at some point we started adding in our evolutionary history lots of tubers and roots Which are not eaten very much by our by our earliest ancestors So we added that to the diet didn't exclude fruit We just added tubers and roots then around two and a half million years ago We started adding meat, which is a lot least for a primate Then we started adding cooked food Of starting maybe around a million years ago and most of us in this room actually get pretty We'll have a serious challenge to actually get enough calories if we don't cook our food Raw foodism can be a real challenge as many of you know And then finally we added small game and fish and all kinds of other things later on This is of course an incomplete list But the point is that the human diet is actually a palimpsest of a whole series of adaptations that evolved over six million years For a variety of different dietary sources and we're all jumbled together in our in our in our in our metabolic system Another important point which is contentious But shouldn't be contentious is that evolution hasn't stopped right the conditions for natural selection still exist There's still variation out there. There's still there's still Heritable variation. There's still differential reproductive success. Look at me versus Mitt Romney, right? His fitness is way higher than mine And and that leaves two conditions for for for natural selection hence for adaptations But the important point I think we all recognize is that culture has become a very important source of evolutionary change It's so rapid. It's so powerful that cultural change now is actually a more powerful force than natural selection But it also interacts with natural selection in ways that we can't appreciate at the moment But in hindsight we will be able to appreciate later on and so there's some classic examples For example the ability to have clothing and fire enable people to inhabit Regions of the world in habitats in which there's not that much vitamin D Supplement of production by the skin at certain parts of the year So there's variation for example in melanin content in different parts of the world That was made possible by culture right in order in order to then drive that selection There's evident evolution of lactase persistence genes Evolved at least five different times in the world in in populations that were producing Daring animals Variations in nose form. I'm kind of obsessed by noses as well as feet Or another example we can talk about that in the bar definitely in the bar And then finally I would make the case again I think this is not Something that's contentious in this audience Which is that many symptoms that are treated by traditional medicine are actually adaptations Feverers for example are an adaptation to help fight infection And so when we immediately just throw analgesics into a feverish kids body We're actually not necessarily helping them fight that infection I would argue that a lot of musculoskeletal pains are adaptations shin splints are a problem that we need to treat Right, they're actually a signal that to your body that you're running like an idiot right and that you should And that you should stop running that way nausea It's all very unpleasant, but it kind of reminds you that perhaps you shouldn't eat that again or to help get rid of Of various toxins in your body. These are all adaptations and we'll talk about some examples of that a little bit on But we have to recalibrate people's minds out there to stop treating symptoms and start actually treating those symptoms as actually real adaptations So it therefore follows that there are a few symbols to the question of what are humans adapted for and this leads to a number of Basic statements and I think For example, there is no one paleo diet. They're probably multiple paleo diets There are not all ancestral adaptations are good for us and many of them involve trade-offs And there are a lot of novel behaviors for which we were not selected that aren't necessarily bad for us either And I think that I'm sure there'll be lots of discussion about these issues over the coming coming coming few days So I'd like to then apply this these these issues of physical inactivity to isn't an amazing slide. Yeah My uh, it's on the web but My colleague Irene Davis who's here keeps using this and I thought I have to use it too because it's such a good one But physical inactivity of course is a very major problem today and and it raises some interesting questions Right. Why is it for example that physical activity is so beneficial to health? But in and almost everybody knows that a healthy body is related to a healthy mind And that activity is important for health And why is it that even when people know that they hate to exercise anyway, right? So in order to try to answer those questions from an adaptive perspective I'd like to give you a very brief history evolutionary history of physical activity very brief Talk about its consequences today for health and then try to talk about an adaptive adaptive perspective using those principles that I just outlined So let's wind the clock and clock back and we could go back, you know Millions and millions and millions of years a useful starting point is when we diverged from the other apes around six to eight Million years ago and our last common ancestor with chimpanzees lived somewhere in africa probably in the margins of a rainforest And it's a contentious issue But I would argue very strongly that that creature was much like a chimpanzee not completely like a chimpanzee But probably a knuckle walker a fruit eating Fruit eating ape that was probably both very good at climbing, but also occasionally was terrestrial That's a contentious issue But it doesn't really matter the important point is that we do have a number of these very first hominins The creatures that are more closely related to us than to chimpanzees Sahelanthropists, which I've worked on a roaring and this wonderful artypithecoskeleton Chairman over here And what's interesting about these critters is that they're all what we call facultative bipeds Facultative means that they're capable of bipedalism, but they didn't walk like you and me and it wasn't all they did Right. They were not habitual bipeds. They may not even have been committed by pets There's a lot of debate about just what they were doing and how they were what kind of bipeds they were But the question that's important for us is why were they bipeds in the first place? And the answer is probably because of climate change the period in which humans Human in the chimpanzee lineage split was the end of a period called the myosine which ended around Five million years ago and that was a period of major global cooling This is the earth's temperature for the last few million years and as the world cooled There was a major shift in in Habitat distribution in Africa and we had A loss in fragmentation of forests and the growth of woodland habitats Now if you're an ape who likes to eat ripe fruit and the forests around you start disappearing That presents a bit of an adaptive challenge for you And bipedalism may have been an important response to that climate change So one hypothesis is that bipedalism wasn't initially a postural adaptation for feeding in trees And that's not an unreasonable hypothesis And another hypothesis they're not necessarily mutually exclusive was that it affects the cost of locomotion We call it the cost of transport which is how much oxygen it takes to move a kilo of your body a meter And it turns out that knuckle walking which we think was characteristic of the last common answer Is extremely costly way of locomoting chimpanzee spends four times as much energy To schlep a kilo of its body the same distance as you and I do And that's because they have very crouched postures And they're always basically it's like they're groucho marks all day long And they're paying for a lot of muscle cost to keep their body from collapsing against the ground So by becoming bipedal we may have been able to reduce that highly flexed postural locomotor posture and save a lot of energy so humans spend about a quarter of the energy So even if they weren't completely like you and me they still might have saved some energy And so intermediate stages still could have been adaptive So in a resource change when when fruits for example become less densely distributed and more patchy For the same amount of energy so chimps go about two to three kilometers They walk about two to three kilometers a day cost them about 600 calories a day But the same amount of energy a human can go eight to 12 kilometers a day And you can easily appreciate why that might have been an adaptive benefit So the important point is that we became good at walking long distances economically But it came at a very substantial cost So I was just in the airport and I saw the replays of Usain Bolt's spectacular 1068 run which translates to he ran 10.38 meters per second He can do that both the hundred meters and he can do a little bit slower for the 200 meters But Usain Bolt the world's fastest human can only do that for Less than 30 seconds your average chimpanzee can run twice as fast as Usain Bolt and can do it for a few minutes By becoming bipedal we lost the ability to gallop immediately meant we became slow We basically halved our speed because we can lose less force against the ground We also lost a lot of agility and skill just think about what a chimpanzee can do And what a human can do There's no question that a chimpanzee in the olympics would easily win any acrobatic competition If you could get it to stick its landing, but it probably wouldn't Wouldn't give a hoot about sticking a landing Anyway, but that's another story All right, so we became bipeds at a great cost, but for some advantages So so early on in human evolution. We became long-distance walkers probably I think But that got intensified in a second transition which occurred between between about four and two million years ago with the australopithecine So many of you know lucy, but lucy is one of a large and complex family And if you want to take You know a class in human evolution You can learn all about the differences between australopithecus this and australopithecus that and it's very boring The important point to note is that these are varied responses to a wide variety of habitats But they generally appear to be open habitats and to make a complex story more simple and generally The the australopithecine seem to be more Adapted to eating a mechanically demanding diet So we basically they weaned us off fruit and started eating lots of tubers and more fallback foods and less high quality foods But in addition they seem to have been very good at walking at least most of them But they also retained lots of abilities to climb in trees So that happened for a few million years and our ancestors lived in Africa eating roots and tubers and living in trees But then a major shift occurred again starting around two and a half million years ago with the origins of the genus homo And the really transitional important species to think about is homo erectus all of us in this room are the way we are today Because of this species homo erectus I think one of the most pivotal species in human evolution And its origin also comes from a major climatic shift around three to two million years ago Was when the ice age started as the polar ice caps formed in the north and the south hemispheres It sucked a lot of moisture out of the That was that was being Provided to Africa There was a lot of drying in Africa and it meant that forests started giving way to more savanna like habitats It was when Africa really became much more open And and a lot of these resources started disappearing and so of course if you're homo erectus You want to know what's for dinner back then you're probably thinking well I guess I'll have to eat that rather than that right and that's essentially what happened The solution to this climatic change was really the evolution of hunting and gathering complex evolutionary shift But really it involves a number of features behavioral strategies that are all combined together One of them of course is making stone tools and processing food So we have some of the oldest stone tools for example right now are dated to 2.6 million years ago from northern Kenya These are they We also have Evidence that there must have been cooperation and some kinds of food sharing a division of labor That's another story. We certainly know that meat started being incorporated much more in the diet back then Now chimpanzees eat a little bit of meat, but but but but home erectus must have been eating quite a bit more meat We have for example, this uh, this is the oldest known Fossil with clear butchery marks. It's been also bashed open to remove marrow It's 2.6 million years old and of course in order to get these kinds of resources in a habitat like this You have to move around a lot and today hunter gathers about the same body mass as these early home erectuses Have to walk between 9 and 15 kilometers a day for the same kind of diet probably It's reasonable to infer that home erectus probably also had to walk between 9 and 15 kilometers a day And in fact, we see in the body of home erectus all kinds of adaptations for this kind of what I would call endurance athleticism Doesn't mean we gave up the ability to have some kind of power and skill But we lost a lot of that again when we transitioned from from chimpanzees But we have in the home erectus body lots of adaptations for endurance running We have lots of adaptations for long distance walking. We think we see adaptations for throwing There's all kinds of things and again, that's another lecture really So but the important point is that hunting and gathering was an incredibly successful adaptive suite of behaviors It because it provided reliable energy to hominin Mothers and fathers and children right and it led to a lot of other shifts So once the hunting and gathering evolves, that's when we begin to see really substantial increases in brain size It's actually after the origin of the genus homo that brain size seems to shoot up And and that's of course necessary because of energy brains are very costly just sitting here Even if you're not listening to me, you're using like 20 25 of your metabolism Just paying for your expensive brain just to sit there in your head If you think by the way, you're not actually using much more energy. Um, but that's another story And then of course later on we got all kinds of other adaptations that were probably made possible by increased cognition fire projectile technology, etc, etc, etc, etc And then finally last and probably least actually is homo sapiens We evolved about 200 000 years ago and actually Disappointing as it may seem we're actually not all that different from our closest ancestors Our brains are about the same size But our heads are maybe reorganized our faces are smaller tucked in there aren't their brains, etc, etc But those that's not really all that important for today What is important to note is that earliest humans were still hunter-gathers not that unlike homo erectus Sure, they had but they had more technology and they seem to have more proclivity and ability to invent new technology and slowly slowly Since humans have evolved we've been adding adding not replacing but adding more technologies to our suite of behaviors Now it's impossible to come up with a simple Description of what hunter-gatherers do hunter-gatherers vary enormously from from from the temperate environments to equatorial environments From from from asia africa of the new world There's an enormous amount of variation in what hunter-gatherers do But if you try to sort of stand back from all the all the noise And look at what the what the what the essential signal is that hunter-gatherers in general tend to be very active Right, they tend to walk long distances a day the worldwide average for hunter-gatherers is nine kilometers a day for females And 15 kilometers a day for males Some but not all hunter-gatherer groups participate in some amount of running Hunter-gatherer groups have to do digging they have to carry they have to climb trees They have to schlep stuff babies food, etc There's they have to prepare food they have to make tools hunter-gatherers basically have to be athletes Use their bodies all day long From for most of their life so they have to start when they're young There's differences between different populations as to when kids have to start participating in in forging activities And they have to continue to do so until they until they die There's no such thing as retirement when you're a hunter-gatherer There's no such thing as a Sabbath either you have to work day in day out all your life And it's only very recently even it's not really the origins of humans that change this It's really farming an industry that changed this lifestyle really substantially So how is this affected physical activity? Well, there are many different ways to measure physical activity And a very common and a simple one is to look at to use pals physical activity levels Which is the ratio of the total amount of energy you're expending versus divided by your basal metabolic rates So when you're asleep and drugged out in the bed right and if you're in bed rest your pal is about 1.2 If you're a typical sedentary office worker like this guy your pal is probably about 1.5 Well, he plays basketball regularly. So he's probably a little bit higher And if you're like doing the tour de France your pal can be pretty extraordinary, but usually about about 2.5. That's that's pretty high So there's been a lot of effort to try to measure physical activity levels among hunter-gatherers There's lots of different estimates up there. It's actually a paper that came out last week from Some former students of mine that measured it in the haza hunter-gatherers But in general if you look across the literature, there's a more or less agreement that hunter-gatherers tend to have Physical activity levels about 1.9 1.8, but there's a range 1.6 to 2.2 And subsistence farmers have to work pretty hard to actually a little bit harder Again, there's a big range 1.6 to 2.4, but basically until until recently There's been a high levels of activity We have good data on physical activity levels in industrialized society and develops Difference between developed and less developed nations, but there's been about an 8% reduction on average Within origins of industrialization. So early industrialists had to work pretty hard But the big shift really is modern Post-industrial lives, right where there's been now another 14% reduction into people with modern office jobs And again, it differs a little bit between developed and less developed nations That's a pretty big reduction about 15% if you ask how much is a 15% reduction in a physical activity level mean? Well, if you are a typical american and you're you're basically ingesting vast amounts of You know calorie rich food you might have about a total energy expenditure about 3000 or totally energy input Sorry, that's the incorrect slide there about 3000 calories a day if your expenditure is about 2500 calories a day That's a shift of 450 calories a day does not take very long with that kind of positive energy balance go from there to there And we know that this exacts an enormous toll on health There's a lot of effort now to try to figure out how much physical inactivity costs us in health Different studies come up with different results. This is a very famous study from 2004 Which didn't separate physical inactivity from diet Actually, it's very hard of course to separate physical inactivity from dietary sources because they so often co-vary But as you can see it's a second leasing cause of death in the united states It's physical activity and diet and one recent study just came out actually arguing that it's actually greater Contribute to to to a death and morbidity and illness than than diet And that needs to be of course resolved So there are lots of studies that have tried to measure this and perhaps I think one of the most impressive is the as the aerobic center longitudinal study Which many of you are probably familiar with it's been headed by steve blair And they've looked at more than 80 000 patients over a very very long time period at the cooper clinic And it's involved with physical exams and coronary scans and body composition and bloody bloody bloody blah They've been surveying all the deaths what causes people to die Lots and lots of information from this study And this is if there's any one slide that encapsulates the results of the study It's this one. It's this shows this is a deaths per 10 000 years in many years And it's been adjusted for by various kinds of risk factors such as age and exam year etc And it's divided the group into three cardiovascular Cardiorespiratory fitness groups low moderate and high and the number of risk factors such as whether you smoke If you have high blood pressure high levels of cholesterol and you can see there's a big dose effect of exercise Especially if you have a lot of risk factors Now what does this actually mean in terms of actual numbers? Well Here's a way of looking at the data if you are unfit versus always fit You have about a three times greater rate of cardiovascular death by cardiovascular disease And if you look at all cos mortality again, it's about three times higher between those who are unfit versus fit And remember this has been adjusted for all the other variables in the study So if you ever want evidence that being fitness really helps your health, this is it Now if you ask most american women out there If you could they could you could tell them something that would reduce their their risk of breast cancer by 50% Most people would pay good money for that And I actually we already know how to reduce your risk risk of breast cancer by 50% It's caused because it's called exercise right There's actually a more than two fold reduction in risk After again, you adjust for age and bmi smoking alcohol intake etc etc Between individuals in the study who are low fitness versus high fitness That's it's pretty remarkable data and it's actually a travesty that more people don't know that information It's not more well well broadcast Okay, so now I don't need to convince you folks in this room that physical activity is important for health The question is how can an evolutionary perspective on adaptation understand these effects? Well an obvious again the first and most obvious statement is that again many modern illnesses are mismatch conditions caused by novel behaviors for which We're not adaptive right so we evolved as I made the argument many diverse adaptations to be athletes And that physical inactivity is from a from a from a physical perspective both abnormal and pathological It's abnormal and pathological not to be physically active There are many examples of it one example for example is osteoporosis Your bone your musculoskeletal system requires Stress in order to grow properly if you remain inactive when you're young you don't develop as much bone mass So then when you start losing bone mass, which is inevitable as you age You you you lose mass and if you've sedentary you don't gain as much mass and you lose it more rapidly And more than 50 percent of women today who are all over the age of 50 I believe I think that's the statistic now are at risk of osteoporosis the numbers and men are climbing And osteoporosis fractures are a major cause of mortality and morbidity among elderly populations It's a very serious risk and the only way to solve that is to get people to exercise when they're young So by not allowing and not having more physical activity in schools We're essentially condemning entire generation of individuals in this country to to to risk of osteoporosis And that's just one of many musculoskeletal systems If you look throughout the body from the brain the nervous system the immune system the endocrine system the reductive system They're all affected very strongly by reproductive by by physical activity Now the second point I made was that adaptations don't always evolve to promote fitness Always evolve to promote fitness, but not necessarily health and a good example That would be why we need to exercise in order to be fit I mean why not simply have natural selection of adapter bodies to be fit all the time Why do you have to go through this exercise crap to to you know raise your vo2? Why not just why didn't natural selection just adapt to the body to have a high vo2? So we didn't have to to to sweat and run around the river and you know Do whatever it is go to the gym or whatever it is We have to do go through all that turmoil right in order to try to be fit Well the answer is that That that's because of an adaptive set of systems a set of adaptive systems That body doesn't want to waste energy on things that don't promote reproduction. So excess capacity is actually costly So the body is designed to match capacity with demand for fitness so that when you become inactive the body's designed down regulated It's just simply evolution never expected us to downregulate it as much as so many people today. Look at all you by the way You're all sitting. It's terrible. You should be getting up and exercising while I'm talking So so so this is it. So again our our loss of ability to maintain Our inability to maintain fitness without stress is because of an adaptive system That is designed not to promote health but to promote reproduction It's just channel energy away from reproduction away from from maintaining costly structures like muscles Which can consume 40 percent of your metabolism and divert it towards pumping out more babies Another important point is there was no single environment of evolutionary adaptiveness, right? The bodies of palimpsestive adaptations and that I think explains why this that some conflicting evidence about why we like to and don't like to exercise now Hunter gathers Probably don't have much selection to enjoy exercise because they don't have any choice It's not like you get up in the day and your mother says don't forget to exercise and eat a healthy diet when you're hunter gather You have no choice but to exercise and eat a healthy diet because that's all there is right So they would love probably just like many people today to live this kind of fantasy life But that's really their reality life. And if you ever go visit for foragers, you'll see that when they're not out there foraging They take it easy, right? They're actually on the threshold of energy balance They don't have a lot of extra calories to burn And so they spend a lot of time doing nothing when they don't have to do anything That's actually adaptive now that said remember the bodies of palimpsestive adaptations And we also have adaptations to make us love exercising and one of them is the endocannabinoid system So if you exercise and by the way, if anybody wants to go for a barefoot run tomorrow We can meet say at seven o'clock at the john harvard statue and we can go for a good hard 50-minute run and we can all get high for the rest of the day Because that run will increase our concentrations of endocannabinoids in our bloodstream and also actually up regulate the receptor activity in the brain And there's lots of really cool evidence about that. So again, there's a complex of adaptations We like to be lazy, but we also have reinforcements for being fit Don't forget again that evolution hasn't stopped But remember that my fifth prince fourth principle was that cultural evolution is now Overwhelming natural selection and a good example of that is whether or not Is the evidence that people who live very unfit lives are not actually paying a price in terms of reproductive success So this poor kid who I grabbed off the web Probably as he grows up he's going to need all these medicines He'll need insulin and metformin because he's going to get type 2 diabetes He's going to need statins and beta blockers and diuretics and probably heart surgery for for his failed cardiovascular system. He's going to probably get he probably already has Gastrointestinal reflux disease He's going to need purple crack and he's going to need orthotics and joint replacements and all that kind of stuff But is that going to affect his reproductive fitness? Of course not It's going to affect your your wallet because you have to pay for all that Think about the two trillion dollars we spend the united states on on medicine But it doesn't affect people's reproductive success. And so we have to remember that and then finally Symptoms are actually adaptations, right? We know that when you eat all these carbohydrates There's really basically two ways you can do do that if you're very active you can store a little bit of as glycogen But not that much It's actually why I like to run marathons because I really like to like to glycogen load And but for rest of us or when you're not doing that, of course you go straight to fat And of course it's obvious to anybody who takes an evolutionary perspective That's storing excess energy as fat as an adaptation that shouldn't be contentious at all But and but it follows then that obesity is not a disease It's a symptom of a long-term energy imbalance and that's the real disease and we have to keep that in mind We need to help other people understand that So in short thinking about the complexities of adaptation Helps us evaluate critically how to use information about human evolution to promote health and well-being And I obviously physical activity is just one example and I hope that these principles of adaptation have helped Set a We'll provide one of I think probably many frameworks that we'll we'll prop up over the next few days The final issue of course is what can we do and what should we do? How much should we use carrots? How much should we use sticks to to to deal with this problem? I know there are some very passionate opinions out there and I'm definitely not going to talk about them today That's not even probably a topic for the bar because we'll just start to Just arguing but actually let's talk about the bar, but that's another election So with that I just want to say thank you I think this is a it's a real pleasure to be here and I look forward to the next few days and I really think that What really needs to happen is that this movement, which is really now a grassroots movement has to has to also become A larger movement from the top down that's going to take a lot of work and it's going to have to start from Symposia like this. So it's a real honor to be here. Thank you very much Any two questions while we start to set up the next talk Hi, I thought your talk was great. I hope the slides might be available afterwards. I gave it to somebody. So, yes, great Unless I'm mistaken I didn't hear the word epigenetics in your talk and I'm interested in the multi-generational implications of paleo And I wonder if you could say a few words about how intelligent diet and lifestyle choices Can have implications for our epigenetic gene expression fantastic question So obviously any time there's a genetic any any effect of Environment on the body Is epigenetic now there are two different definitions of epigenetic out there I'm being an old-school biologist. I use the famous definition of conrad Waddington, which is that it's any environmental influence on on on a cell And so I consider epigenetics to be all the gene environment interactions that occur in your body Why different cells in your body are different from each other? But there's another definition for epigenetics, which is the long-term heritable effects of non-genetic Shifts both are very important We don't know to what extent the the latter which is suspect what you're asking about has has major implications on Population scale health, but certainly they do there are studies from from, you know There are effects their genetic their epigenetic effects on for example metabolism that can last multiple generations that occur because of Complex ways that affect how DNA is transcribed so methylation for example was These little methyl molecules that combine to DNA and turn off their transcription So there are a lot of interesting effects. I think we're at the tip of the iceberg and understanding that For example many cancers may be A result of this kind of epigenetic effect in fact heritabilities of cancers could be not because of genes but because of non-genetic heritable but non-genetic information It's a great question, but I don't think there's a lot of good answers at the moment now, but there's research is necessary I have a question about exercise So a lot of the ways of quantitative exercise have to do with energy and caloric expenditure versus intake But meanwhile if you compare exercise or in paleolithic paleolithic times to what we do in a gym We have a lot of mechanical repetitive restricted behaviors that are not Really developing agility. They're not on a variable landscape. They have all kinds of rigid things that don't develop intelligence in the same way as Having a combination of activities all at once that require a much more integrated use of our brains So i'm wondering from a scientific point of view if you have any any experience with Quantitating that complexity of human activity more comprehensively Oh, wow, uh, that's a great question. I would take an entire symposium to answer There's no question human bodies adapted for a wide and diverse range of activities and the kinds of things that people do in gyms are I suspect often cause injury because as you say they're repetitive So for example on a treadmill every step is exactly the same as any other step and that leads to Probably leads to the incidence of repetitive stress injuries lots of Machines that work your muscles, right only work them in a kind of an an abnormal way And so they lead to high rates of injury, you know, if you go to a gym and somebody has to teach you how to use the machine why not just Use the gym and do something a little bit more natural and um, but so yes, there's a there's a there's a complex set of Questions about what's natural exercise? What's the best way to exercise? What's the right? Distribution of exercise activities for optimal health and and and it's effect on the brain for the for that matter You know, I would add barefoot running because when you get you lose all that sensory Perception when you wear a shoe that certainly affects your brain. I mean there's it's a complex issue One that is very poorly explored, but But worth studying All right. Thank you very much